Diagnosis & Treatment of Other Rare Blood Disorders

At Memorial Sloan Kettering, in addition to diagnosing and treating myeloproliferative diseases (or myeloproliferative neoplasms), we have expertise in other rare blood conditions such as histiocytosis, paroxysmal nocturnal hemoglobinuria, and systemic mastocytosis.


This group of rare diseases, characterized by the presence of an abnormally high number of white blood cells called histiocytes, can be difficult to diagnose.

The symptoms are common physical problems not specific to these diseases, including pain, fever, rash, and frequent urination. Symptoms depend on where the tumors form as well as the organs and systems involved and their functions. Tumors in weight-bearing bones, such as the legs or spine, may cause the bones to fracture without apparent reason. Histiocytes can also form small tumors in the mouth and gums and on the skin.

Diagnosis may come through x-rays or other imaging methods, blood tests, or biopsies of tumors and bone marrow. Depending on the extent of the disease, our doctors may use chemotherapy, low doses of radiation therapy, or surgery to treat skin or bone tumors caused by histiocytosis.

The most common form of histiocytosis is Langerhans cell histiocytosis. Research has revealed that tumors occurring in Langerhans cell histiocytosis — as well as in a rare form of histiocytosis called Erdheim-Chester disease (ECD) — often have mutations in a gene called BRAF V600. The protein produced by this mutated gene has been shown to promote the growth of other cancers such as melanoma and some lung cancers.

Memorial Sloan Kettering researchers are investigating other genetic alterations in addition to BRAF V600 that may be present in patients with ECD. They are also seeking to identify the type of cell in which ECD originates and find the optimal targeted therapy for treating patients with the BRAF V600 mutation. We also are conducting a clinical trial exploring a new treatment option for people with Langerhans cell histiocytosis and ECD.

Paroxysmal Nocturnal Hemoglobinuria

At Memorial Sloan Kettering, we use one of two blood tests to diagnose paroxysmal nocturnal hemoglobuinuria (PNH), a rare disease in which red blood cells break down earlier than normal: the Ham test or flow cytometry.

The Ham test checks whether red blood cells become more fragile when they are placed in mild acid. Flow cytometry is a technique for counting and examining microscopic particles by suspending them in a stream of fluid and passing them by an electronic detection apparatus. The technique is used to measure certain proteins associated with PNH in order to diagnose the disease.

In some cases we treat PNH patients with blood transfusion, folic acid, and, if appropriate, iron supplements. If you have low levels of red blood cells, platelets, and white cells, we may recommend that you take steroids or the same immunosuppressive drugs used to treat aplastic anemia, which include cyclosporine and anti-thymocyte globulin.

Blood clots are usually treated with anticoagulants and sometimes, if severe, with a drug called tissue plasminogen activator (known as tPA), which can rapidly dissolve the clots.

PNH can be cured by bone marrow transplantation. This procedure should be considered on an individual basis, based on the patient’s age and symptoms.